Cooling system pressure

ROY · 11-08-2012, 01:26 PM

I'm having an issue I have never heard of or had experience with.My cooling system [SBF]is maintaining a high pressure even after long periods of shut down[weeks]! I noticed external weeping of coolant at the bottom of the heads and at the ends of the intake manifold.I checked the expansion tank,it was empty!I went to open the radiator cap so I could drain the system,it had enough pressure to blow the cap up as I turned it,it hit the stops then puked fluid!I pulled the intake and heads[aluminum],no signs of blown gaskets! Any ideas? I'm lost on this one! ROY.

Lew Silverman · 11-08-2012, 03:17 PM

Roy,

The system is designed to run "under pressure", so the first place I'd look would be at the cap to make sure it was relieving that pressure, above the PSI rating on the cap into the overflow container. If you can get a hold of a cooling system tester - Stant used to make a good one, but so does Mac, Snap-on and Cornwell, it will make the diagnostic's easier.

I run a 7 PSI cap on my 'wagon, which gives me just enough pressure to ensure proper cooling.

Good Luck!

Lew

Rsmith38 · 11-08-2012, 05:09 PM

Autozone rents presure testers around here. They charge your CCard then refund the charge when you return it. The tester has a couple of adapters so you can test the cap - thats where I'd look first.

race watcher · 11-08-2012, 05:39 PM

I have run into this problem in the past.. What I found most of the time I had an air pocket somewhere in the cooling system.

rod · 11-09-2012, 11:55 PM

the cap is obviously good, or it would not hold pressure that long. there would not be any leaks in the cooling system or it would not hold pressure that long. most likely an air pocket in the system somewhere. you may have to raise the front of the car way up to get it to 'burp'. after the season is over, pull the 'stat and drill at least one 'air bleed' hole in the 'stat housing.

rod in AZ

ROY · 11-10-2012, 01:25 AM

Thank You everyone that gave suggestions.I do not run a T-stat,so no restriction there.The air pocket makes sense,even though I fill the system slowly and with the upper hose off at the radiator and turned so as to be the highest point in the system.I spoke with two engine builders today,they both said it had to be blown head gaskets even though the gaskets do not show any damage!! ROY.

Ed Wright · 11-10-2012, 09:55 AM

I would pressure check the cap. May not be releasing at the proper pressure. Five to seven psi would be plenty. I actually don't run any pressure in mine. I just cut a small "V" in the rubber gasket. Never a problem. I jack the front of my car up when I fill the cooling system, and run my electric water pump while topping it off.

Alex Denysenko · 11-11-2012, 07:27 PM

the only time I have evetr seen this on a SBF is when someone installed the head gaskets backwards.

Dwight Southerland · 11-12-2012, 09:21 AM

Quote:

Originally Posted by Ed Wright

I would pressure check the cap. May not be releasing at the proper pressure. Five to seven psi would be plenty. I actually don't run any pressure in mine. I just cut a small "V" in the rubber gasket. Never a problem. I jack the front of my car up when I fill the cooling system, and run my electric water pump while topping it off.

I was going to suggest a "no pressure system". I have always used a cap that seals at the top but no pressure mechanism. There are advantages.

Wade_Owens · 11-12-2012, 02:12 PM

Quote:

Originally Posted by Dwight Southerland

I was going to suggest a "no pressure system". I have always used a cap that seals at the top but no pressure mechanism. There are advantages.

x2

Wade

11-08-2012, 01:26 PM	#1
ROY Junior Member Join Date: Oct 2007 Posts: 15 Likes: 0 Liked 0 Times in 0 Posts	Cooling system pressure I'm having an issue I have never heard of or had experience with.My cooling system [SBF]is maintaining a high pressure even after long periods of shut down[weeks]! I noticed external weeping of coolant at the bottom of the heads and at the ends of the intake manifold.I checked the expansion tank,it was empty!I went to open the radiator cap so I could drain the system,it had enough pressure to blow the cap up as I turned it,it hit the stops then puked fluid!I pulled the intake and heads[aluminum],no signs of blown gaskets! Any ideas? I'm lost on this one! ROY.

11-08-2012, 03:17 PM	#2
Lew Silverman VIP Member Join Date: Mar 2010 Location: Newport News, VA Posts: 1,435 Likes: 371 Liked 129 Times in 59 Posts	Re: Cooling system pressure Roy, The system is designed to run "under pressure", so the first place I'd look would be at the cap to make sure it was relieving that pressure, above the PSI rating on the cap into the overflow container. If you can get a hold of a cooling system tester - Stant used to make a good one, but so does Mac, Snap-on and Cornwell, it will make the diagnostic's easier. I run a 7 PSI cap on my 'wagon, which gives me just enough pressure to ensure proper cooling. Good Luck! Lew __________________ Lew Silverman #2070 "The Wagon Master" N/SA

11-08-2012, 05:09 PM	#3
Rsmith38 Member Join Date: Mar 2011 Posts: 186 Likes: 0 Liked 28 Times in 15 Posts	Re: Cooling system pressure Autozone rents presure testers around here. They charge your CCard then refund the charge when you return it. The tester has a couple of adapters so you can test the cap - thats where I'd look first.

11-08-2012, 05:39 PM	#4
race watcher Junior Member Join Date: Nov 2006 Posts: 50 Likes: 5 Liked 1 Time in 1 Post	Re: Cooling system pressure I have run into this problem in the past.. What I found most of the time I had an air pocket somewhere in the cooling system.

11-09-2012, 11:55 PM	#5
rod Member Join Date: Dec 2009 Location: Kingman, NW AZ. in the middle of the longest stretch of Route 66 Posts: 313 Likes: 0 Liked 20 Times in 15 Posts	Re: Cooling system pressure the cap is obviously good, or it would not hold pressure that long. there would not be any leaks in the cooling system or it would not hold pressure that long. most likely an air pocket in the system somewhere. you may have to raise the front of the car way up to get it to 'burp'. after the season is over, pull the 'stat and drill at least one 'air bleed' hole in the 'stat housing. rod in AZ

11-10-2012, 01:25 AM	#6
ROY Junior Member Join Date: Oct 2007 Posts: 15 Likes: 0 Liked 0 Times in 0 Posts	Re: Cooling system pressure Thank You everyone that gave suggestions.I do not run a T-stat,so no restriction there.The air pocket makes sense,even though I fill the system slowly and with the upper hose off at the radiator and turned so as to be the highest point in the system.I spoke with two engine builders today,they both said it had to be blown head gaskets even though the gaskets do not show any damage!! ROY.

11-10-2012, 09:55 AM	#7
Ed Wright Veteran Member Join Date: Mar 2005 Location: Sand Springs, OK Posts: 8,132 Likes: 896 Liked 390 Times in 170 Posts	Re: Cooling system pressure I would pressure check the cap. May not be releasing at the proper pressure. Five to seven psi would be plenty. I actually don't run any pressure in mine. I just cut a small "V" in the rubber gasket. Never a problem. I jack the front of my car up when I fill the cooling system, and run my electric water pump while topping it off. __________________ Ed Wright 4156 SS/JA

11-11-2012, 07:27 PM	#8
Alex Denysenko Senior Member Join Date: Jan 2002 Location: Michigan City IN Posts: 633 Likes: 0 Liked 4 Times in 3 Posts	Re: Cooling system pressure the only time I have evetr seen this on a SBF is when someone installed the head gaskets backwards. __________________ Alex Denysenko NHRA 3038 SS, 3305 STK - IHRA 6 SS, 330A STK Moneymaker Racing LaPorte Indiana 219-861-1214 www.moneymakerracing.net